Refrigerator

ABSTRACT

A refrigerant circuit ( 10 ) is formed by connecting, in the order given, a compressor ( 11 ), a four-way selector valve ( 12 ), an outdoor heat exchanger ( 13 ), an expansion valve ( 14 ), and an indoor heat exchanger ( 15 ) by a gas side pipe ( 31 ) and a liquid side pipe ( 32 ). The refrigerant circuit ( 10 ) is charged with a single refrigerant of R32 or with an R32/R125 mixed refrigerant whose R32 content is not less than 75% by weight. As an insulating material of an electric motor of the compressor ( 11 ), a resin material is used, and as an refrigeration oil a synthetic oil is used. When cooling rated capacity is not more than 5 kW, the liquid side pipe ( 32 ) is formed by use of a pipe whose inside diameter is less than 4.75 mm.

TECHNICAL FIELD

The present invention relates to refrigeration systems. Moreparticularly, this invention relates to a refrigeration system whichemploys either a single refrigerant of R32 or an R32 containing mixedrefrigerant.

BACKGROUND ART

A conventional refrigeration system has been known which comprises arefrigerant circuit including a compressor, a condenser, a pressurereducing mechanism, and an evaporator and the refrigerant circuit formsa refrigeration cycle using an HCFC refrigerant such as R22. Of theseelement devices of the refrigerant circuit, the compressor plays animportant role of increasing the pressure of the refrigerant. Therefore,refrigeration oil is required for smooth operation of the compressor.

On the other hand, refrigeration systems employing an HFC refrigerantuse a synthetic oil as a refrigeration oil.

Problems that the Invention Intends to Solve

However, such a synthetic oil is degraded when contaminated with air andmoisture, thereby causing a problem of increasing the total acid numberof the synthetic oil. On the other hand, resin materials have beenutilized as an insulating material for an electric motor of thecompressor. However, the resin materials undergo deterioration instrength (for example, deterioration in tensile strength) during therise in total acid number. This may cause burning out of the electricmotor in the worst case.

Further, for the case of using a resin material such as polyethyleneterephthalate (PET), it is the resin material itself that causeshydrolysis during the rise in temperature due to refrigerationoperations, when coexisting with moisture. As a result, thedeterioration of the resin material will be aggravated.

Contamination with air and moisture occurs at the time of manufacture ofthe element devices of the refrigerant circuit and at the time ofinstallation of the system in the field. Therefore, the amount of suchcontamination can be reduced by making a change in the manufacturemethod and process and by reinforcing the product quality control at thetime of manufacture of the system. On the other hand, at the time ofinstallation of the system, it is necessary to take some measures forachieving improvements in the degree of ultimate vacuum when drawingvacuum, for extending the length of time taken to draw vacuum, and forproviding improvements in vacuum pump performance.

Therefore, with respect to refrigeration systems provided with acompressor, there is the demand for further improvements in systemreliability as well as in system handling ease.

Bearing in mind the aforementioned problems, the present invention wasmade. Accordingly, an object of the present invention is to provideimprovements in system reliability as well as in system handling ease.

DISCLOSURE OF THE INVENTION

With a view to achieving the aforesaid object, the present inventionutilizes a resin material as an insulating material for use in anelectric motor of a compressor and employs a refrigerant of lesspressure loss (e.g., an R32 single refrigerant or R32 mixed refrigerant)in comparison with the R22 or the like.

The present invention was made based on the following reasons. That is,by reason of the fact that an R32 single refrigerant (or an R32 mixedrefrigerant) provides a greater refrigeration effect in comparison withR22, R407C, and R410A, less amounts of circulating refrigerant necessaryfor obtaining the same capacity are required in comparison with, forexample, the R22. Therefore, for the case of the R32 single refrigerant(or the R32 mixed refrigerant), its pressure loss is smaller incomparison with, for example, the R22, when flowing through a flowpathof the same diameter.

The refrigerant pipe includes a liquid side pipe. The liquid side pipeis a pipe extending, for example, from a condenser outlet to anevaporator inlet. The liquid side pipe does not cause a drop in thesystem performance even when there is an increase in the pressure loss,as long as that increase falls within the control range of the pressurereducing mechanism (for example a capillary tube and an expansionvalve). Further, when employing an R32 single refrigerant or an R32mixed refrigerant, the high-low pressure difference in the refrigerantcircuit is, at most, about 1.6 times greater than when the R22refrigerant is employed. Correspondingly, the allowable range forrefrigerant pressure loss extends. Accordingly, when the R32 singlerefrigerant (or the R32 mixed refrigerant) is employed, it is possibleto further reduce the diameter of the liquid side pipe thanconventional, without a drop in the system performance.

On the other hand, the refrigerant pipe further includes a dischargepipe and a suction pipe. The discharge pipe is a pipe extending, forexample, from a compressor discharge side to a condenser inlet, whereasthe suction pipe is a pipe extending, for example, from an evaporatoroutlet to a compressor suction side. The pressure loss of thesedischarge and suction pipes considerably affects the system performance.However, the utilization of the R32 single refrigerant (or the R32 mixedrefrigerant) decreases the pressure loss to a further extent thanconventional. This shows that, even when the diameter of the dischargeand suction pipes is reduced, the utilization of an R32 singlerefrigerant (or an R32 mixed refrigerant) makes it possible to maintainthe same system performance as conventional. Furthermore, the R32 singlerefrigerant (or the R32 mixed refrigerant) makes it possible to reducethe pipe diameter to some extent while maintaining superiority inperformance to conventional systems.

Further, as an element which affects the performance of a heatexchanger, saturation temperature difference equivalent to the amount ofrefrigerant pressure loss becomes important. For the case of the R32single refrigerant (or the R32 mixed refrigerant), the pressure loss issmall. Therefore, even when the diameter of a heat transfer pipe of theheat exchanger is reduced, the saturation temperature difference canbecome the same as conventional. Furthermore, both the R32 singlerefrigerant and the R32 mixed refrigerant have a higher heat transferrate than conventional. Therefore, even when a heat transfer pipe has areduction in diameter, it is able to maintain the heat exchangingcapacity at high levels.

From the above, the inventor of the present invention found out that,even when an R32 single refrigerant (or an R32 mixed refrigerant) isemployed to reduce the diameter of a refrigerant pipe and the diameterof a heat exchanger heat transfer pipe for reducing the internal volumeof a refrigerant circuit, there occurs no problem with the systemperformance at all. On the other hand, the amount of air or moisturecontamination in a refrigerant circuit increases in proportion to theinternal volume of a refrigerant circuit. Therefore, in accordance withthe present invention, the internal volume of a refrigerant circuit isreduced by utilization of an R32 single refrigerant (or an R32 mixedrefrigerant) so that the amount of air or moisture contamination whichis introduced into the refrigerant circuit can be reduced, and thedeterioration of an insulating material used in an electric motor of thecompressor is prevented.

HFC refrigeration systems employ a synthetic oil as a refrigeration oil.As a synthetic oil, there are ether oil and ester oil havingcompatibility with refrigerant. And, other than these synthetic oils,there is alkylbenzene oil which exhibits poor compatibility withrefrigerant but is able to secure the performance of returning oil byviscosity reduction.

In comparison with mineral oil used in conventional R22 refrigerationsystems, the synthetic oil is more susceptible to chemical reaction suchas decomposition, polymerization and so forth, when the refrigerantcircuit is contaminated with air or moisture. As a result of this, partof the synthetic oil is deposited in the form of a sludge in anexpansion valve or in a capillary tube, which may cause clogging of aflowpath of the refrigerant circuit.

More specifically, ether oil and alkylbenzene oil are susceptible tooxidative deterioration by air and ester oil is hydrolyzed whencontaminated with moisture. As a result, the total acid number of eachsynthetic oil increases.

On the other hand, insulating material such as insulating paper, a leadwire, a tying cord, or the like has been utilized for compressorelectric motors. Such an insulating material is a resin material. Theinsulating material is for example polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polyphenylene sulfide (PPS),polybutylene terephthalate (PBT), polyether ether ketone (PEEK),polyamide imide (PAI), or polyimide.

Any of these resin materials undergoes a drop in strength, e.g., a dropin tensile strength, during the rise in total acid number. This may giverise to burning out of the electric motor.

Further, for the case of PET, PEN, and PBT, their molecules containtherein ester bonds. Because of this, when existing together withmoisture, these resin materials themselves cause hydrolysis during therise in temperature by refrigeration operations. As a result, thedeterioration of the resin materials will be aggravated to a furtherextent.

Therefore, as described above, in the present invention an R32 singlerefrigerant (or an R32 mixed refrigerant) is employed to reduce theinternal volume of a refrigerant circuit. Because of this, the amount ofair or moisture contamination in the refrigerant circuit can be reduced.Because of such a reduction in the amount of air or moisturecontamination, the deterioration of an insulating material for anelectric motor of a compressor can be prevented.

More specifically, in accordance with an invention of the presentapplication, either an R32 single refrigerant or a mixed refrigerantwhose R32 content is not less than 75% is employed and a resin materialis utilized as an insulating material for an electric motor in acompressor (11).

Another invention is directed to a refrigeration system whose coolingrated capacity is not more than 5 kW, the refrigeration systemcomprising a refrigerant circuit (10) which forms a refrigeration cyclein which either an R32 single refrigerant or a mixed refrigerant whoseR32 content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material. And, the refrigerant circuit (10) includes a liquidside pipe (32) which is formed by use of a pipe whose inside diameter isless than 4.75 mm.

Still another invention is directed to a refrigeration system whosecooling rated capacity is not more than 5 kW, the refrigeration systemcomprising a refrigerant circuit (10) which forms a refrigeration cyclein which either an R32 single refrigerant or a mixed refrigerant whoseR32 content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material. And, the refrigerant circuit (10) includes a liquidside pipe (32) which is formed by use of a pipe whose inside diameterranges from 3.2 mm to 4.2 mm.

A further invention is directed to a refrigeration system whose coolingrated capacity is not more than 5 kW, the refrigeration systemcomprising a refrigerant circuit (10) which forms a refrigeration cyclein which either an R32 single refrigerant or a mixed refrigerant whoseR32 content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material. And, the refrigerant circuit (10) includes a liquidside pipe (32) which is formed by use of a pipe whose inside diameterranges from 3.5 mm to 3.9 mm.

A still further invention is directed to a refrigeration system whosecooling rated capacity is not more than 5 kW, the refrigeration systemcomprising a refrigerant circuit (10) which forms a refrigeration cyclein which either an R32 single refrigerant or a mixed refrigerant whoseR32 content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material. And, the refrigerant circuit (10) includes a liquidside pipe (32) which is formed by use of a pipe whose inside diameterranges from 3.6 mm to 3.8 mm.

Another invention is directed to a refrigeration system whose coolingrated capacity is greater than 5 kW but not more than 18 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or a mixedrefrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a liquid side pipe (32) which is formed by use ofa pipe whose inside diameter is less than 7.92 mm.

Still another invention is directed to a refrigeration system whosecooling rated capacity is greater than 18 kW but not more than 22.4 kW,the refrigeration system comprising a refrigerant circuit (10) whichforms a refrigeration cycle in which either an R32 single refrigerant ora mixed refrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a liquid side pipe (32) which is formed by use ofa pipe whose inside diameter is less than 11.1 mm.

A further invention is directed to a refrigeration system whose coolingrated capacity is greater than 5 kW but not more than 22.4 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or a mixedrefrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a liquid side pipe (32) which is formed by use ofa pipe whose inside diameter ranges from 5.4 mm to 7.0 mm.

A still further invention is directed to a refrigeration system whosecooling rated capacity is greater than 5 kW but not more than 22.4 kW,the refrigeration system comprising a refrigerant circuit (10) whichforms a refrigeration cycle in which either an R32 single refrigerant ora mixed refrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a liquid side pipe (32) which is formed by use ofa pipe whose inside diameter ranges from 5.7 mm to 6.7 mm.

Another invention is directed to a refrigeration system whose coolingrated capacity is greater than 5 kW but not more than 22.4 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or a mixedrefrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a liquid side pipe (32) which is formed by use ofa pipe whose inside diameter ranges from 6.0 mm to 6.4 mm.

Still another invention is directed to a refrigeration system whosecooling rated capacity is so designed as to be greater than 22.4 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or a mixedrefrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a liquid side pipe (32) which is formed by use ofa pipe whose inside diameter is less than 13.88 mm.

A further invention is directed to a refrigeration system whose coolingrated capacity is so designed as to be greater than 22.4 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or a mixedrefrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a liquid side pipe (32) which is formed by use ofa pipe whose inside diameter ranges from 7.5 mm to 9.8 mm.

A still further invention is directed to a refrigeration system whosecooling rated capacity is so designed as to be greater than 22.4 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or a mixedrefrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a liquid side pipe (32) which is formed by use ofa pipe whose inside diameter ranges from 7.8 mm to 9.5 mm.

Another invention is directed to a refrigeration system whose coolingrated capacity is so designed as to be greater than 22.4 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or a mixedrefrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a liquid side pipe (32) which is formed by use ofa pipe whose inside diameter ranges from 8.1 mm to 9.1 mm.

Still another invention is directed to a refrigeration system whosecooling rated capacity is not more than 3.2 kW, the refrigeration systemcomprising a refrigerant circuit (10) which forms a refrigeration cyclein which either an R32 single refrigerant or a mixed refrigerant whoseR32 content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material. And, the refrigerant circuit (10) includes a gasside pipe (31) which is formed by use of a pipe whose inside diameter isless than 7.92 mm.

A further invention is directed to a refrigeration system whose coolingrated capacity is greater than 3.2 kW but not more than 5 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or amixed, refrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a gas side pipe (31) which is formed by use of apipe whose inside diameter is less than 11.1 mm.

A still further invention is directed to a refrigeration system whosecooling rated capacity is greater than 5 kW but not more than 9 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or a mixedrefrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a gas side pipe (31) which is formed by use of apipe whose inside diameter is less than 13.88 mm.

Another invention is directed to a refrigeration system whose coolingrated capacity is greater than 9 kW but not more than 18 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or a mixedrefrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a gas side pipe (31) which is formed by use of apipe whose inside diameter is less than 17.05 mm.

Still another invention is directed to a refrigeration system whosecooling rated capacity is greater than 18 kW but not more than 22.4 kW,the refrigeration system comprising a refrigerant circuit (10) whichforms a refrigeration cycle in which either an R32 single refrigerant ora mixed refrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a gas side pipe (31) which is formed by use of apipe whose inside diameter is less than 23.4 mm.

A further invention is directed to a refrigeration system whose coolingrated capacity is so designed as to be greater than 22.4 kW, therefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either an R32 single refrigerant or a mixedrefrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material. And, the refrigerantcircuit (10) includes a gas side pipe (31) which is formed by use of apipe whose inside diameter is less than 26.18 mm.

A still further invention is directed to a refrigeration systemcomprising a refrigerant circuit (10) which includes (a) a compressor(11) which utilizes a resin material as an electric motor insulatingmaterial and (b) an indoor heat exchanger (15) and forms a refrigerationcycle in which either an R32 single refrigerant or a mixed refrigerantwhose R32 content is not less than 75% is used as a refrigerant. And,the indoor heat exchanger (15) includes a heat transfer pipe which isformed by use of a heat transfer pipe whose inside diameter is less than5.87 mm.

Another invention is directed to a refrigeration system comprising arefrigerant circuit (10) which includes (a) a compressor (11) whichutilizes a resin material as an electric motor insulating material and(b) an outdoor heat exchanger (13) and forms a refrigeration cycle inwhich either an R32 single refrigerant or a mixed refrigerant whose R32content is not less than 75% is used as a refrigerant. And, the outdoorheat exchanger (13) includes a heat transfer pipe which is formed by useof a heat transfer pipe whose inside diameter is less than 6.89 mm.

Still another invention is directed to a refrigeration system comprisinga refrigerant circuit (10) which includes (a) a compressor (11) whichutilizes a resin material as an electric motor insulating material and(b) an outdoor heat exchanger (13) and forms a refrigeration cycle inwhich either an R32 single refrigerant or a mixed refrigerant whose R32content is not less than 75% is used as a refrigerant. And, the outdoorheat exchanger (13) includes a heat transfer pipe which is formed by useof a heat transfer pipe whose inside diameter is less than 7.99 mm.

Further, the compressor (11) may use a synthetic oil as a refrigerationoil.

Furthermore, the liquid side pipe (32) may be a liquid side connectingpipe for connecting an indoor unit (17) and an outdoor unit (16).

Further, the gas side pipe (31) may be a gas side connecting pipe forconnecting an indoor unit (17) and an outdoor unit (16).

Furthermore, preferably the mixed refrigerant is an R32/R125 mixedrefrigerant.

Finally, the refrigerant may be an R32 single refrigerant.

EFFECTS OF THE INVENTION

Therefore, the present invention makes it possible to reduce theinternal volume of the refrigerant circuit (10), thereby making itpossible to reduce the amount of air contamination, moisturecontamination, or other contamination which is introduced into therefrigerant circuit (10). As a result, it is possible to preventinsulating materials used in the electric motor in the compressor (11)from undergoing deterioration. Therefore, burning out of the electricmotor can be prevented and, in addition, a sliding portion of thecompressor (11) is prevented from undergoing abrasion and seizing.Further, the expansion mechanism such as a capillary tube can beprevented from clogging, for example. Accordingly, it is possible toachieve the reduction in fraction defective.

Furthermore, since the possibility that the refrigerant circuit (10) iscontaminated with air or other contaminants is small, this facilitatesmanufacture and install control, thereby making it possible to provideimprovements in manufacture ease and installation ease.

Further, the use of a synthetic oil as a refrigeration oil makes itpossible to provide improvements in system reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigerant circuit diagram of an air conditioning system.

FIG. 2 is a Mollier diagram.

FIG. 3 is a table showing calculation results for the heat transferpipe's inside diameter ratio.

FIG. 4 is a cross-sectional view of a pipe with grooves.

FIG. 5 is another Mollier diagram.

FIG. 6 is a table showing calculation results for the liquid side pipe'sinside diameter ratio.

FIG. 7 is a diagram showing R22 gas side pipe diameters and R22 liquidside pipe diameters with respect to the cooling rated capacity.

FIG. 8 is a diagram showing the reduced diameter ratio of a gas sidepipe to a liquid side pipe with respect to the cooling rated capacity.

FIG. 9 is a diagram showing an R22 copper pipe versus R32 copper piperelationship.

FIG. 10 is a table showing global warming potentials.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described inconjunction with the Figures.

Construction of the Air Conditioning System

As seen in FIG. 1, a refrigeration system of the present embodiment isan air conditioning system (1) formed by connection of an outdoor unit(16) which is a heat source unit and an indoor unit (17) which is autilization unit. A refrigerant circuit (10) of the air conditioningsystem (1) employs, as its refrigerant, either a single refrigerant ofR32 (hereinafter referred to as the R32 single refrigerant) or a mixedrefrigerant comprising R32 and R125 in which the R32 content is not lessthan 75% but less than 100% by weight (i.e., an R32 composition richmixed refrigerant which is hereinafter called the R32 /R125 mixedrefrigerant).

The refrigerant circuit (10) is a refrigerant circuit which forms avapor compression refrigeration cycle. The refrigerant circuit (10) isformed by connecting, in series in the order given, a compressor (11), afour-way selector valve (12), an outdoor heat exchanger (13) which is aheat source side heat exchanger, an expansion valve (14) which is anexpansion mechanism, and an indoor heat exchanger (15) which is autilization side heat exchanger, by a gas side pipe (31) and a liquidside pipe (32). These pipes (31) and (32) are refrigerant pipes.

More specifically, a discharge side of the compressor (11) and a firstport (12 a) of the four-way selector valve (12) are connected togetherby a first gas side pipe (21). A second port (12 b) of the four-wayselector valve (12) and the outdoor heat exchanger (13) are connectedtogether by a second gas side pipe (22). The outdoor heat exchanger (13)and the expansion valve (14) are connected together by a first liquidside pipe (25). The expansion valve (14) and the indoor heat exchanger(15) are connected together by a second liquid side pipe (26). Theindoor heat exchanger (15) and a third port (12 c) of the four-wayselector valve (12) are connected together by a third gas side pipe(23). A fourth port (12 d) of the four-way selector valve (12) and asuction side of the compressor (11) are connected together by a fourthgas side pipe (24).

The compressor (11), the first gas side pipe (21), the four-way selectorvalve (12), the second gas side pipe (22), the outdoor heat exchanger(13), the first liquid side pipe (25), the expansion valve (14), and thefourth gas side pipe (24) are all housed in an outdoor unit (16),together with an outdoor air blower (not shown). On the other hand, theindoor heat exchanger (15) is housed in an indoor unit (17), togetherwith an indoor air blower (not shown). A part of the second liquid sidepipe (26) and a part of the third gas side pipe (23) constitute aso-called connecting pipe for establishing connection between theoutdoor unit (16) and the indoor unit (17).

In the compressor (11), a synthetic oil is used as a refrigeration oil.Such a synthetic oil comprises ether oil, ester oil, or the like. Otherthan these synthetic oils, alkylbenzene oil may be used.

Further, the refrigeration oil is added with an extreme pressureadditive. As an extreme pressure additive, additives of the phosphorusfamily such as phosphoric ester and phosphite may be used. Other thanthese phosphorus family additives, additives of the chlorine family andadditives of the sulfur family may be used.

On the other hand, an electric motor (not shown) of the compressor (11)is housed in the casing. In the electric motor, insulating material suchas insulating paper, a lead wire, a tying cord and the like is used.Such an insulating material comprises a resin material. And, theinsulating material comprises polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polyphenylene sulfide (PPS),polybutylene terephthalate (PBT), polyether ether ketone (PEEK),polyamide imide (PAI), polyimide, or the like.

That is, the insulating paper, the lead wire, and the typing cord areformed by use of these resin materials. For example, the insulatingpaper may be formed of PET and the lead wire may be formed of PPS, andplural types of resin materials may be utilized in the compressorelectric motor.

Ether oil and alkylbenzene oil are susceptible to oxidativedeterioration by air. Ester oil is hydrolyzed by moisture contamination.As a result, the total acid number of any of the synthetic oilsincreases.

Any of these resin materials undergoes a drop in strength such as a dropin tensile strength during the rise in total acid number. This may giverise to burning out of the electric motor in the worst case.

Further, for the case of PET, PEN, and PBT, their molecules containtherein ester bonds. Because of this, when existing together withmoisture, these resin materials cause hydrolysis when the temperaturerises by refrigeration operations. As a result, the deterioration of theresin materials will be aggravated.

On the other hand, the refrigeration oil is added with an extremepressure additive for the prevention of abrasion and seizing of asliding part of the compressor (11). Particularly, since refrigerants ofthe HFC family such as R32 contain no chlorine atom, there is no extremepressure action. Therefore, an extreme pressure additive is added to therefrigeration oil.

Such an extreme pressure additive is hydrolyzed when a sliding surfaceof the compressor (11) is at high temperatures and when existingtogether with moisture and, as a result, there is a drop in thelubricity. As a result, the extreme pressure additive may be depositedin the form of a sludge in the expansion valve (14). Further,chlorine-family extreme pressure additives may produce a corrosivesubstance.

Therefore, as will be described later, an R32 single refrigerant (or anR32/R125 mixed refrigerant) is used to diminish the internal volume ofthe refrigerant circuit (10), for reducing the amount of air or moisturecontamination.

Construction of the Heat Exchanger

Since the R32 single refrigerant (or the R32/R125 mixed refrigerant)exhibits a greater refrigeration effect per unit volume than that of theR22, the former requires a less amount of circulating refrigerant forachieving a specified capacity in comparison with the later. Therefore,for the case of the R32 single refrigerant (or the R32/R125 mixedrefrigerant), the amount of circulating refrigerant can be reduced,provided that heat exchanger's heat transfer pipes of the same insidediameter are used. As a result, the loss of tube pressure becomessmaller in comparison with the R22.

Generally, if the inside diameter of a heat transfer pipe of the heatexchanger is made smaller, this results in a decrease in the heattransfer area and in an increase in the refrigerant pressure loss,thereby causing a drop in the total system performance. However, whenusing an R32 single refrigerant (or an R32/R125 mixed refrigerant), itsrefrigerant side heat transfer rate in the heat transfer pipe is largerthan that of R22, so that it is possible to achieve the same totalperformance as R22 or a better total performance than R22, even when theloss of tube pressure is increased up to about an R22 equivalent level.

On the other hand, of all the devices of the refrigerant circuit (10),it is the outdoor heat exchanger (13) which holds a largest amount ofrefrigerant. Accordingly, if the diameter of the heat transfer pipe ofthe outdoor heat exchanger (13) is reduced, this makes it possible toeffectively reduce the amount of charging refrigerant. Further, such areduction in the heat transfer pipe diameter results in a decrease inthe internal volume of the refrigerant circuit (10). Furthermore, byvirtue of the reduction of the heat transfer pipe diameter, both theoutdoor heat exchanger (13) and the indoor heat exchanger (15) becomesmaller in size, thereby making it possible to promote the compacting ofthe outdoor unit (16) and indoor unit (17).

Therefore, in the air conditioning system (1) of the present invention,the diameter of the heat transfer pipes of the outdoor heat exchanger(13) and indoor heat exchanger (15) is reduced to such an extent thatthe loss of tube pressure is at the same level as the R22. Morespecifically, in the air conditioning system (1) of the presentinvention, the amount of variation in the refrigerant saturationtemperature corresponding to the amount of pressure loss in the heattransfer pipe is taken into account and the inside diameter dimension ofthe outdoor heat exchanger (13) and indoor heat exchanger (15) is set sothat the temperature variation amount becomes the same as that of theR22.

Basic Principle of Construction of the Heat Transfer Pipe

Next, a basic principle of constituting heat transfer pipes for theoutdoor and indoor heat exchangers (13) and (15) will be described indetail.

Here, as shown in FIG. 2, each heat transfer pipe for the outdoor andindoor heat exchangers (13) and (15) is set such that the saturationtemperature variation ΔTe corresponding to the pressure loss ofevaporation refrigerant becomes the same as that of R22 in aconventional system. That is,ΔTe=Const.  (1)Here,

-   -   ΔP: pipe pressure loss (kPa)    -   L: pipe length (m)    -   G: refrigerant circulation amount (kg/s)    -   A: flowpath cross-sectional area (m²)    -   λ: loss coefficient    -   d: pipe inside diameter (m)    -   ρs: compressor suction refrigerant density (kg/m³)        And, the saturation temperature variation ΔTe is given by the        following expression.        ΔTe={ΔT/ΔP}×ΔPe  (2)

The pressure loss ΔP is calculated using the following expression whichis a friction loss expression for annular pipes.ΔP=λ·L/d·G ²/2·ρs·A ²  (3)

If the cooling capacity Q=G×Δh is constant, then:ΔP∝G²/ρs·d⁵∝(Δh²·ρs·d⁵)⁻¹  (4)

where Δh is the refrigeration effect (kJ/kg).

Therefore, the following expression is derived from the expressions (2)and (4).ΔTe∝{ΔT/ΔP}×(Δh²·ρs·d⁵)⁻¹  (5)

Hence, from the expressions (1) and (5) and from the material propertyvalues of R22 and R32, the inside diameter ratio of an R32 heat transferpipe to an R22 heat transfer pipe, i.e., the heat transfer pipe diameterreducing ratio, can be found by the following expression.{ΔT/ΔP} ₂₂×(Δh ₂₂ ² ·ρs ₂₂ ·d ₂₂ ⁵)⁻¹ ={ΔT/ΔP} ₃₂×(Δh ₃₂ ² ·ρs ₃₂ ·d ₃₂⁵)⁻¹ d ₃₂ /d ₂₂=((Δh ₃₂ /Δh ₂₂)² ×ρs ₃₂ /ρs ₂₂×({ΔT/ΔP}₃₂ /{ΔT/ΔP}₂₂)⁻¹)^(−1/5)  (6)

Referring to FIG. 3, there are shown results of calculations found bysubstitution of each material property value into the expression (6). Inthe calculations, it is assumed that the evaporation temperature Te is 2degrees Centigrade and the condensation temperature Tc is 49 degreesCentigrade, and the evaporator outlet super heat SH=5 degrees Centigradeand the condenser outlet sub cool SC=5 degrees Centigrade.

The calculation results show that the diameter of the R32 heat transferpipe can be reduced about 0.76 times that of the R22 heat transfer pipe.Further, the calculation results show that the diameter of the R32/R125heat transfer pipe can be reduced about from 0.76 to 0.8 times that ofthe R22 heat transfer pipe. The same calculations were performed onother replacement refrigerants for reference and the calculation resultsshow that none of them achieved better diameter reduction than the R32(see FIG. 3).

In the air conditioning system (1) of the present embodiment, based uponthe aforesaid principle, heat transfer pipes having the following insidediameters are employed, for comparison with the R22 heat transfer pipe.

That is, when an R32 single refrigerant is used, the heat transfer pipeof the indoor heat exchanger (15) is formed by use of a heat transferpipe whose inside diameter is in the range of 4.7 mm to 5.9 mm, whereasthe heat transfer pipe of the outdoor heat exchanger (13) is formed byuse of a heat transfer pipe whose inside diameter is in the range of 5.4mm to 6.7 mm.

On the other hand, when an R32/R125 mixed refrigerant is used, the heattransfer pipe of the indoor heat exchanger (15) is formed by use of aheat transfer pipe whose inside diameter is in the range of 4.7 mm to6.2 mm, whereas the heat transfer pipe of the outdoor heat exchanger(13) is formed by use of a heat transfer pipe whose inside diameter isin the range of 5.4 mm to 7.1 mm.

If the inside diameter of each heat transfer pipe falls below thenumerical value range, the loss of refrigerant pressure excessivelyincreases, although the charging amount of refrigerant is reducedfurther. On the other hand, the inside diameter of each heat transferpipe exceeds the numerical value range, the effect of R32 such as theeffect of reducing the amount of charging refrigerant is reduced,although the loss of refrigerant pressure decreases and there isimprovement in the system efficiency.

Therefore, in order to maintain a balance between them, in the presentembodiment the inside diameters of the heat transfer pipes of theoutdoor and indoor heat exchangers (13) and (15) are so set as to fallin the aforesaid numerical value ranges.

Of course, there may be made further restrictions on the numerical valueranges for allowing R32 to exhibit its characteristics moresignificantly, depending upon the system use condition or othercondition.

For example, when an R32 single refrigerant is used, the heat transferpipe of the indoor heat exchanger (15) may be formed by use of a heattransfer pipe whose inside diameter is in the range of 4.9 mm to 5.7 mm,whereas the heat transfer pipe of the outdoor heat exchanger (13) may beformed by use of a heat transfer pipe whose inside diameter is in therange of 5.6 mm to 6.5 mm.

Further, when an R32 single refrigerant is used, the heat transfer pipeof the indoor heat exchanger (15) may be formed by use of a heattransfer pipe whose inside diameter is in the range of 5.1 mm to 5.5 mm,whereas the heat transfer pipe of the outdoor heat exchanger (13) may beformed by use of a heat transfer pipe whose inside diameter is in therange of 5.8 mm to 6.3 mm.

On the other hand, when an R32/R125 mixed refrigerant is used, the heattransfer pipe of the indoor heat exchanger (15) may be formed by use ofa heat transfer pipe whose inside diameter is in the range of 4.9 mm to6.0 mm, whereas the heat transfer pipe of the outdoor heat exchanger(13) may be formed by use of a heat transfer pipe whose inside diameteris in the range of 5.6 mm to 6.9 mm.

Further, when an R32/R125 mixed refrigerant is used, the heat transferpipe of the indoor heat exchanger (15) may be formed by use of a heattransfer pipe whose inside diameter is in the range of 5.2 mm to 5.7 mm,whereas the heat transfer pipe of the outdoor heat exchanger (13) may beformed by use of a heat transfer pipe whose inside diameter is in therange of 5.9 mm to 6.6 mm.

Here, by “the inside diameter of a heat transfer pipe” for the case ofinternal side smoothed pipes is meant a pipe inside diameter after pipeexpansion. Further, as shown in FIG. 4, by “the inside diameter of aheat transfer pipe” for the case of internal side grooved pipes is meanta value which is a remainder of subtracting from the outside diameterafter pipe expansion a value which is twice the bottom thickness, i.e.,the inside diameter di=do−2t.

Various heat transfer pipes, such as a pipe made of copper or aluminum,are available. The outdoor and indoor heat exchangers (13) and (15) ofthe present embodiment are each formed by a plate fin tube heatexchanger comprising a copper pipe and an aluminum fin as an air heatexchanger capable of exchanging heat with air. Therefore, their heattransfer pipes are each formed by use of a copper pipe.

Construction of the Refrigerant Pipe

Further, in the air conditioning system (1) of the present embodiment,not only the diameter of the heat transfer pipes of the heat exchangers(13, 15) but also the diameter of the refrigerant pipe of therefrigerant circuit (10) is reduced in order that the internal volume ofthe refrigerant circuit (10) may be reduced.

As described above, if an R32 single refrigerant (or an R32/R125 mixedrefrigerant) is used intact in an existing R22 refrigerant pipe, theloss of refrigerant pressure is reduced. Therefore, even if the insidediameter of the liquid side pipe (32) of the refrigerant circuit (10) isreduced for increasing the loss of tube pressure to the same level asthe time that R22 is used, this maintains the system performance at thesame level as conventional. Therefore, in the air conditioning system(1), the liquid side pipe (32) has a reduction in diameter to such anextent that the loss of pipe pressure becomes equivalent to that of R22,for reducing the internal volume of the refrigerant circuit (10) whilemaintaining the system performance.

On the other hand, in the present embodiment, the gas side pipe (31) isthe same as a commonly-used R22 gas side pipe. However, in order toprovide a reduction in diameter of the gas side pipe (31), it is morepreferable that the diameter of the liquid side pipe (32) also bereduced.

Basic Principle of Construction of the Refrigerant Pipe

Next, a basic principle of constructing the liquid side pipe (32) willbe described.

Here, the liquid side pipe (32) is designed such that the ratio of thepressure loss of the liquid side pipe (32) to the amount of drop in thepressure of refrigerant from the condenser outlet to the evaporatorinlet is the same as the case of R22. That is, the following expression,in which the signs shown in FIG. 5 are used, holds as follows.(Pco−Pvi)+(Pvo−Pbi)/(Pco−Pei)=Const.  (7)where:

-   -   ΔP: pipe pressure loss (kPa)    -   L: pipe length (m)    -   G: refrigerant circulation amount (kg/s)    -   A: flowpath cross-sectional area (m²)    -   λ: loss coefficient    -   d: pipe inside diameter (m)    -   ρs: compressor suction refrigerant density (kg/m³)        Each term of the numerator of the expression (7) is calculated        using the following expression which is a friction loss        expression for annular pipes.        ΔP=λ·L/d·G ²/2·ρs·A ²  (8)

Here, the capacity Q=G×Δh is constant and the following expression isderived from the expression (8).ΔP∝G ² /ρs·d ⁵∝(Δh ² ·ρs·d ⁵)⁻¹  (9)where:

-   -   Δh: refrigeration effect (kJ/kg)

Therefore, the following expression is derived.(Pco−Pvi)+(Pvo−Pbi)∝(Δh²·ρs·d⁵)⁻¹  (10)And, the following expression is derived from the expressions (7) and(10).(Pco−Pvi)+(Pvo−Pbi)/(Pco−Pei)∝(Δh²ρs·d⁵)⁻¹/(HP−LP)  (11)

Therefore, from the expressions (7) and (11) and from the materialproperty values of R22 and R32, the heat transfer pipe diameter reducingratio of an R32 heat transfer pipe to an R22 heat transfer pipe can befound by the following expression.(Δh ₂₂ ² ·ρs ₂₂ ·d ₂₂ ⁵)⁻¹/(HP ₂₂ −LP ₂₂)=(Δh ₃₂ ² ·ρs ₃₂ d ₃₂ ⁵)⁻¹(HP₃₂ −LP ₃₂) d ₃₂ /d ₂₂=((Δh ₃₂ /Δh ₂₂)² ×ρs ₃₂ /ρs ₂₂×(HP ₃₂ −LP ₃₂)/(HP₂₂ −LP ₂₂)^(−1/5)  (12)

Referring to FIG. 6, there are shown results of calculations found bysubstitution of each material property value into the expression (12).Also in these calculations, the evaporation temperature Te is 2 degreesCentigrade and the condensation temperature Tc is 49 degrees Centigrade,and the super heat SH=5 degrees Centigrade and the sub cool SC=5 degreesCentigrade.

The calculation results show that the diameter of the liquid side pipe(32) of R32 single refrigerant can be reduced about 0.76 times that ofan R22 liquid side pipe. Further, the calculation results show that itis possible to reduce the diameter of the liquid side pipe (32) ofR32/R125 mixed refrigerant about 0.76–0.8 times that of an R22 liquidside pipe if the R32 content is present in an amount of not less than 75wt. %. The same calculations were performed on other replacementrefrigerants for reference and the calculation results shows that noneof them achieved better diameter reduction than the R32 (see FIG. 6).

FIG. 7 is a diagram showing the pipe diameters (inside diameters) of gasside and liquid side pipes per cooling rated capacity in a conventionalsystem using R22.

In the air conditioning system (1) of the present embodiment, accordingto the cooling rated capacity, the gas side pipe (31) is formed by useof a pipe having the same diameter as the aforesaid R22 gas side pipe,whereas the liquid side pipe (32) is formed by use of a pipe having adiameter smaller than that of the R22 liquid side pipe.

FIG. 8 is a diagram showing the ratio of the inside diameter dg of a gasside pipe to the inside diameter dl of a liquid side pipe, i.e., theinside diameter ratio (=the gas side pipe inside diameter dg/the liquidside pipe inside diameter dl). In the air conditioning system (1) of thepresent embodiment, according to the cooling rated capacity, the gasside pipe (31) and the liquid side pipe (32) having the following insidediameter ratios are used.

That is, if the cooling rated capacity is greater than 5 kW but not morethan 9 kW, such a combination of the gas side pipe (31) and the liquidside pipe (32) that the inside diameter ratio is in the range 2.1 to3.5, is used. If the cooling rated capacity is not more than 5 kW ormore than 9 kW, such a combination of the gas side pipe (31) and theliquid side pipe (32) that the inside diameter ratio is in the range 2.6to 3.5, is used.

Further, if the cooling rated capacity is not more than 5 kW, the liquidside pipe (32) is formed by use of a pipe whose inside diameter is inthe range of 3.2 mm to 4.2 mm. If the cooling rated capacity is greaterthan 5 kW but less than 22.4 kW, the liquid side pipe (32) is formed byuse of a pipe whose inside diameter is in the range of 5.4 mm to 7.0 mm.If the cooling rated capacity is not less than 22.4 kW, the liquid sidepipe (32) is formed by use of a pipe whose inside diameter is in therange of 7.5 mm to 9.8 mm.

If the inside diameter ratio or the inside diameter of the liquid sidepipe (32) falls below the aforesaid numerical value range, there is adrop in the system performance, although the refrigerant charging amountis further reduced. On the other hand, the inside diameter ratio or theinside diameter of the liquid side pipe (32) exceeds the aforesaidnumerical value range, the effect of reducing the charging amount ofrefrigerant diminishes, although the refrigerant pressure loss isreduced and the system performance is therefore improved.

To cope with the above problem, in the present embodiment the insidediameters of the gas side pipe (31) and the liquid side pipe (32) areset to fall in the aforesaid numerical value ranges so that therefrigerant charging amount is sufficiently reduced while maintainingthe system performance.

Of course, there may be made further restrictions on the numerical valueranges, depending upon the system use condition or other conditions.

For example, if the cooling rated capacity is greater than 5 kW but notmore than 9 kW, the inside diameter ratio may be so restricted as tofall in the range of 2.4 to 3.2. If the cooling rated capacity is notmore than 5 kW or more than 9 kW, the inside diameter ratio may be sorestricted as to fall in the range of 2.8 to 3.3.

Further, if the cooling rated capacity is greater than 5 kW but not morethan 9 kW, the inside diameter ratio may be so restricted as to fall inthe range from 2.6 to 3.0. If the cooling rated capacity is not morethan 5 kW or more than 9 kW, the inside diameter ratio may be sorestricted as to fall in the range of 2.9 to 3.1.

Further, the inside diameter of the liquid side pipe (32) may be so setas to fall in the range of 3.5 mm to 3.9 mm if the cooling ratedcapacity is not more than 5 kW. If the cooling rated capacity is greaterthan 5 kW but less than 22.4 kW, the inside diameter of the liquid sidepipe (32) may be so set as to fall in the range of 5.7 mm to 6.7 mm. Ifthe cooling rated capacity is not less than 22.4 kW, the inside diameterof the liquid side pipe (32) may be so set as to fall in the range of7.8 mm to 9.5 mm.

Further, the inside diameter of the liquid side pipe (32) may be so setas to fall in the range of 3.6 mm to 3.8 mm if the cooling ratedcapacity is not more than 5 kW. If the cooling rated capacity is greaterthan 5 kW but less than 22.4 kW, the inside diameter of the liquid sidepipe (32) may be so set as to fall in the range of 6.0 mm to 6.4 mm. Ifthe cooling rated capacity is not less than 22.4 kW, the inside diameterof the liquid side pipe (32) may be so set as to fall in the range of8.1 mm to 9.1 mm.

Copper pipes have been used as a refrigerant pipe in many cases becausethey are inexpensive and easy to handle. Since various standardizedcopper pipes are available, it is possible to reduce the cost of therefrigerant pipes (31, 32) by utilizing existing standardized articles.Accordingly, for the purpose of reducing the system cost, both theliquid side pipe (32) and the gas side pipe (31) are preferably formedby combining only standardized articles so that the aforesaid insidediameter ratios are achieved.

FIG. 9 is a diagram for the purpose of comparing the specification of anR22 copper pipe (JISB8607) and that of an R32 high-pressure resistancepipe according to a proposal by Japanese Refrigeration Air ConditioningIndustrial Association.

For the case of the R32 single refrigerant, its best inside diameterratio calculated from the aforesaid calculation results is 0.76,whereas, for the case of the R32/R125 mixed refrigerant whose R32content is 75 wt. %, its best inside diameter ratio is 0.80. FIG. 9shows that the inside diameter ratios can be realized easily bycombinations of standardized articles, if within ±10% of the best insidediameter ratios.

For example, instead of using an R2 standardized pipe of φ9.5 mm, astandardized pipe of φ8.0 mm can be used if R32 is used. The presentembodiment is an embodiment capable of being implemented easily bycombinations of standardized articles.

Operation of the Air Conditioning System

The operation of the air conditioning system (1) will be described basedon the refrigerant circulation operation of the refrigerant circuit(10).

During cooling mode operations, the four-way selector valve (12) is setas indicated by a solid line of FIG. 1. That is, the four-way selectorvalve (12) is placed in such a state that the first port (12 a) isbrought into communication with the second port (12 b) while the thirdport (12 c) is brought into communication with the second port (12 d).

In such a state, gas refrigerant discharged out of the compressor (11),after flowing through the first gas side pipe (21), the four-wayselector valve (12), and the second gas side pipe (22), condenses tochange to liquid refrigerant in the outdoor heat exchanger (13). Theliquid refrigerant, after flowing out of the outdoor heat exchanger(13), flows through the first liquid side pipe (25) and is depressurizedin the expansion valve (14) to change to gas-liquid two-phaserefrigerant. The two-phase refrigerant, after flowing out of theexpansion valve (14), flows through the second liquid side pipe (26).Thereafter, the two-phase refrigerant exchanges heat with indoor air inthe indoor heat exchanger (15) and evaporates to change to gasrefrigerant, whereby the indoor air is cooled. The gas refrigerant,after flowing out of the indoor heat exchanger (15), flows through thethird gas side pipe (23), the four-way selector valve (12), and thefourth gas side pipe (24) and thereafter is drawn into the compressor(11).

On the other hand, during heating mode operations, the four-way selectorvalve (12) is set as indicated by a broken line of FIG. 1. That is, thefour-way selector valve (12) is placed in such a state that the firstport (12 a) is brought into communication with the fourth port (12 d)while the second port (12 d) is brought into communication with thethird port (12 c).

In such a state, gas refrigerant discharged out of the compressor (11),after flowing through the first gas side pipe (21), the four-wayselector valve (12), and the third gas side pipe (23), enters the indoorheat exchanger (15). The refrigerant, which has flowed into the indoorheat exchanger (15), exchanges heat with indoor air in the indoor heatexchanger (15) and condenses to change to liquid refrigerant, wherebythe indoor air is heated. The liquid refrigerant, after flowing out ofthe indoor heat exchanger (15), flows through the second liquid sidepipe (26) and is depressurized in the expansion valve (14) to change togas-liquid two-phase refrigerant. The two-phase refrigerant, afterflowing out of the expansion valve (14), flows through the first liquidside pipe (25) and evaporates to change to gas refrigerant in theoutdoor heat exchanger (13). The gas refrigerant, after flowing out ofthe outdoor heat exchanger (13), flows through the second gas side pipe(22), the four-way selector valve (12), and the fourth gas side pipe(24) and thereafter is drawn into the compressor (11).

Effects of the Embodiment

As described above, in the present embodiment, either an R32 singlerefrigerant or an R32/R125 mixed refrigerant is used as a refrigerantand, in addition, the heat transfer pipes of the outdoor heat exchanger(13) and the indoor heat exchanger (15) and the liquid side pipe (32)each have a further reduction in diameter than conventional. Therefore,in accordance with the present embodiment, it is possible to reduce theinternal volume of the refrigerant circuit (10) while maintaining thesystem performance, and it is possible to suppress contamination, e.g.,moisture contamination and the like, which is introduced into therefrigerant circuit (10).

As a result of the above arrangement, it is possible to prevent thedeterioration of insulating materials used in the electric motor of thecompressor (11). This makes it possible to prevent the electric motorfrom burning out and to prevent a sliding section of the compressor (11)from undergoing abrasion and seizing. Further, the expansion valve (14)can be prevented from undergoing clogging or the like. Accordingly, itis possible to achieve a reduction in the fraction defective.

Furthermore, since the possibility that the refrigerant circuit (10) iscontaminated with air and other contaminants is small, this facilitatesmanufacture and install control of the system, thereby making itpossible to provide improvements in manufacture ease and installationease.

Further, the use of a synthetic oil as a refrigeration oil makes itpossible to provide improvements in system reliability. In other words,circuit clogging due to the deposition of a sludge is unlikely to occureven when a synthetic oil is used as a refrigeration oil, therebyenhancing the reliability of the system. Furthermore, since thepossibility of the refrigerant circuit (10) being contaminated with airand other contaminants is small, this makes it possible to relax qualitycontrol procedures during manufacture and installation.

Further, since the internal volume of the refrigerant circuit (10)becomes smaller, this makes it possible to reduce the amount of chargingrefrigerant. Therefore, the effect of global warming can be reduced.Further, by virtue of the reduction in heat transfer pipe diameter, thecost of the outdoor and indoor heat exchangers (13) and (15) can belowered and the compacting of the outdoor and indoor heat exchangers(13) and (15) can be achieved. Therefore, it becomes possible to reducethe indoor unit (17) and the outdoor unit (16) in size.

Furthermore, since the possibility of the refrigerant circuit (10) beingcontaminated with moisture or other contaminants is small, this preventsan extreme pressure additive added to a refrigeration oil from beinghydrolyzed and prevents a drop in the lubricity. Especially,deteriorated substances hydrolyzed will not be deposited in the form ofa sludge, thereby preventing the flowpath of the refrigerant circuitfrom being clogged, without fail.

Further, it is possible to prevent generation of corrosive substances,such as hydrochloric acid, in an extreme pressure additive of thechlorine family.

Other Embodiments of the Present Invention

In accordance with the present invention, it is, of course, possible toobtain an effect of reducing the internal volume of the refrigerantcircuit (10) by reducing the diameter of both the gas side pipe (31) andthe liquid side pipe (32). However, such an effect can be obtained byreducing only the diameter of the gas side pipe (31).

The gas side pipe (31) which is subjected to reduction in diameter maybe all of the first gas side pipe (21), the second gas side pipe (22),the third gas side pipe (23), and the fourth gas side pipe (24) or someof these gas side pipes. Likewise, the liquid side pipe (32) which issubjected to reduction in diameter may be both the first liquid sidepipe (25) and the second liquid side pipe (26) or one of these liquidside pipes.

On the basis of R22 liquid side pipe values different from those shownin FIG. 7, the diameter (inside or outside diameter) of the liquid sidepipe (32) may be so set as to become smaller than them.

More specifically, the liquid side pipe (32) may be formed by use of apipe whose diameter is less than 4.75 mm, when the cooling ratedcapacity is not more than 5 kW.

Further, the liquid side pipe (32) may be formed by use of a pipe whosediameter is less than 7.92 mm, when the cooling rated capacity isgreater than 5 kW but not more than 18 kW.

Further, the liquid side pipe (32) may be formed by use of a pipe whosediameter is less than 11.1 mm, when the cooling rated capacity isgreater than 18 kW but not more than 22.4 kW.

Further, the liquid side pipe (32) may be formed by use of a pipe whosediameter is less than 13.88 mm, when the cooling rated capacity isgreater than 22.4W.

On the basis of R22 gas side pipe values different from those shown inFIG. 7, the diameter of the gas side pipe (31) may be so set as tobecome smaller than them.

More specifically, the gas side pipe (31) may be formed by use of a pipewhose diameter is less than 7.92 mm, when the cooling rated capacity isnot more than 3.2 kW.

Further, the gas side pipe (31) may be formed by use of a pipe whosediameter is less than 11.1 mm, when the cooling rated capacity isgreater than 3.2 kW but not more than 5 kW.

Further, the gas side pipe (31) may be formed by use of a pipe whosediameter is less than 13.88 mm, when the cooling rated capacity isgreater than 5 kW but not more than 9 kW.

Further, the gas side pipe (31) may be formed by use of a pipe whosediameter is less than 17.05 mm, when the cooling rated capacity isgreater than 9 kW but not more than 18 kW.

Further, the gas side pipe (31) may be formed by use of a pipe whosediameter is less than 23.4 mm, when the cooling rated capacity isgreater than 18 kW but not more than 22.4 kW.

Further, the gas side pipe (31) may be formed by use of a pipe whosediameter is less than 26.18 mm, when the cooling rated capacity isgreater than 22.4 kW.

On the basis of R22 heat transfer pipe values, the diameter of the heattransfer pipe of each of the indoor heat exchanger (15) and the outdoorheat exchanger (13) may be so set as to become smaller than them.

More specifically, the heat transfer pipe of the indoor heat exchanger(15) may be formed by use of a pipe whose inside diameter is less than5.87 mm.

Further, the heat transfer pipe of the outdoor heat exchanger (13) maybe formed by use of a pipe whose inside diameter is less than 6.89 mm.

Further, the heat transfer pipe of the outdoor heat exchanger (13) maybe formed by use of a pipe whose inside diameter is less than 7.99 mm.

The above-described embodiment is intended for air conditioning systemsof a so-called heat pump type capable of selectively performing coolingor heating mode operations. However, the applicability of the presentinvention is not limited to such a heat pump type air conditioningsystem. For example, the present invention is applicable to cooling-onlyair conditioning systems. Further, the present invention is madeapplicable to heating-only air conditioning systems by setting theinside diameter of both the liquid side pipe (32) and the gas side pipe(31) per heating rated capacity corresponding to a cooling ratedcapacity or by setting their inside diameter ratio.

Further, by “cooling rated capacity” used in the aforesaid embodiment ismeant an evaporator capacity. This cooling rated capacity is not limitedto the capacity of an air conditioning system during cooling modeoperations. The cooling rated capacity is a capacity which is exhibitedunder given JIS conditions (e.g., indoor dry-bulb temperature: 27degrees Centigrade; outdoor wet-bulb temperature: 19 degrees Centigrade;and outdoor dry-bulb temperature: 35 degrees Centigrade) where thelength of a connection pipe is 5 m and the difference in level betweenan indoor unit and an outdoor unit is 0 m.

Neither the gas side pipe (31) nor the liquid side pipe (32) isnecessarily formed by use of a copper pipe and these pipes may of coursebe formed of any other pipe such as a SUS pipe, an aluminum pipe, aniron pipe, or the like.

The outdoor heat exchanger (13) and the indoor heat exchanger (13) arenot limited to air heat exchangers and they may be liquid-liquid heatexchangers such as a heat exchanger of the double pipe type.

The refrigeration system of the present invention is not limited torefrigeration systems in a restricted sense. That is, the refrigerationsystem of the present invention includes refrigeration systems in a widesense such as a refrigerator and a dehumidifier, not to mention airconditioning systems.

When the present invention is applied to a refrigeration system capableof accommodating long piping or to a refrigeration system provided witha plurality of indoor units, it is possible to extend the allowablelength of piping. Furthermore, in accordance with the present invention,the number of indoor units can be increased. Accordingly, it becomespossible to provide improvements in system handling ease as well as incommodity property.

When the present invention is applied to a machine capable ofaccommodating long piping or to a machine capable of accommodating aplurality of indoor units, it is possible to provide an extendedallowable piping length. Furthermore, the present invention enables thenumber of indoor units to increase. Accordingly, it becomes possible toprovide improvements in system handling ease as well as in commodityproperty.

Further, in the present invention, the refrigeration oil is notnecessarily added with an extreme pressure additive.

INDUSTRIAL APPLICABILITY

As has been described above, the refrigeration system of the presentinvention is useful for cases utilizing either an R32 single refrigerantor an R32/R125 mixed refrigerant, and the present invention is suitableparticularly for a refrigeration system utilizing resin material.

1. A refrigeration system whose cooling rated capacity is not more than5 kW, said refrigeration system comprising a refrigerant circuit (10)which forms a refrigeration cycle in which either a single refrigerantof R32 or a mixed refrigerant whose R32 content is not less than 75% isused as a refrigerant and includes a compressor (11) which utilizes aresin material as an electric motor insulating material, wherein saidrefrigerant circuit (10) includes a liquid side pipe (32) which isformed by use of a pipe whose inside diameter is less than 4.75 mm.
 2. Arefrigeration system whose cooling rated capacity is not more than 5 kW,said refrigeration system comprising a refrigerant circuit (10) whichforms a refrigeration cycle in which either a single refrigerant of R32or a mixed refrigerant whose R32 content is not less than 75% is used asa refrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material, wherein saidrefrigerant circuit (10) includes a liquid side pipe (32) which isformed by use of a pipe whose inside diameter ranges from 3.2 mm to 4.2mm.
 3. A refrigeration system whose cooling rated capacity is not morethan 5 kW, said refrigeration system comprising a refrigerant circuit(10) which forms a refrigeration cycle in which either a singlerefrigerant of R32 or a mixed refrigerant whose R32 content is not lessthan 75% is used as a refrigerant and includes a compressor (11) whichutilizes a resin material as an electric motor insulating material,wherein said refrigerant circuit (10) includes a liquid side pipe (32)which is formed by use of a pipe whose inside diameter ranges from 3.5mm to 3.9 mm.
 4. A refrigeration system whose cooling rated capacity isnot more than 5 kW, said refrigeration system comprising a refrigerantcircuit (10) which forms a refrigeration cycle in which either a singlerefrigerant of R32 or a mixed refrigerant whose R32 content is not lessthan 75% is used as a refrigerant and includes a compressor (11) whichutilizes a resin material as an electric motor insulating material,wherein said refrigerant circuit (10) includes a liquid side pipe (32)which is formed by use of a pipe whose inside diameter ranges from 3.6mm to 3.8 mm.
 5. A refrigeration system whose cooling rated capacity isgreater than 5 kW but not more than 18 kW, said refrigeration systemcomprising a refrigerant circuit (10) which forms a refrigeration cyclein which either a single refrigerant of R32 or a mixed refrigerant whoseR32 content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material, wherein said refrigerant circuit (10) includes aliquid side pipe (32) which is formed by use of a pipe whose insidediameter is less than 7.92 mm.
 6. A refrigeration system whose coolingrated capacity is greater than 18 kW but not more than 22.4 kW, saidrefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either a single refrigerant of R32 or amixed refrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material, wherein saidrefrigerant circuit (10) includes a liquid side pipe (32) which isformed by use of a pipe whose inside diameter is less than 11.1 mm.
 7. Arefrigeration system whose cooling rated capacity is greater than 5 kWbut not more than 22.4 kW, said refrigeration system comprising arefrigerant circuit (10) which forms a refrigeration cycle in whicheither a single refrigerant of R32 or a mixed refrigerant whose R32content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material, wherein said refrigerant circuit (10) includes aliquid side pipe (32) which is formed by use of a pipe whose insidediameter ranges from 5.4 mm to 7.0 mm.
 8. A refrigeration system whosecooling rated capacity is greater than 5 kW but not more than 22.4 kW,said refrigeration system comprising a refrigerant circuit (10) whichforms a refrigeration cycle in which either a single refrigerant of R32or a mixed refrigerant whose R32 content is not less than 75% is used asa refrigerant and includes 10 a compressor (11) which utilizes a resinmaterial as an electric motor insulating material, wherein saidrefrigerant circuit (10) includes a liquid side pipe (32) which isformed by use of a pipe whose inside diameter ranges from 5.7 mm to 6.7.mm
 9. A refrigeration system whose cooling rated capacity is greaterthan 5 kW but not more than 22.4 kW, said refrigeration systemcomprising a refrigerant circuit (10) which forms a refrigeration cyclein which either a single refrigerant of R32 or a mixed refrigerant whoseR32 content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material, wherein said refrigerant circuit (10) includes aliquid side pipe (32) which is formed by use of a pipe whose insidediameter ranges from 6.0 mm to 6.4 mm.
 10. A refrigeration system whosecooling rated capacity is so designed as to be greater than 22.4 kW,said refrigeration system comprising a refrigerant circuit (10) whichforms a refrigeration cycle in which either a single refrigerant of R32or a mixed refrigerant whose R32 content is not less than 75% is used asa refrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material, wherein saidrefrigerant circuit (10) includes a liquid side pipe (32) which isformed by use of a pipe whose inside diameter is less than 13.88 mm. 11.A refrigeration system whose cooling rated capacity is so designed as tobe greater than 22.4 kW, said refrigeration system comprising arefrigerant circuit (10) which forms a refrigeration cycle in whicheither a single refrigerant of R32 or a mixed refrigerant whose R32content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material, wherein said refrigerant circuit (10) includes aliquid side pipe (32) which is formed by use of a pipe whose insidediameter ranges from 7.5 mm to 9.8 mm.
 12. A refrigeration system whosecooling rated capacity is so designed as to be greater than 22.4 kW,said refrigeration system comprising a refrigerant circuit (10) whichforms a refrigeration cycle in which either a single refrigerant of R32or a mixed refrigerant whose R32 content is not less than 75% is used asa refrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material, wherein saidrefrigerant circuit (10) includes a liquid side pipe (32) which isformed by use of a pipe whose inside diameter ranges from 7.8 mm to 9.5mm.
 13. A refrigeration on system whose cooling rated capacity is sodesigned as to be greater than 22.4 kW, said refrigeration systemcomprising a refrigerant circuit (10) which forms a refrigeration cyclein which either a single refrigerant of R32 or a mixed refrigerant whoseR32 content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material, wherein said refrigerant circuit (10) includes aliquid side pipe (32) which is formed by use of a pipe whose insidediameter ranges from 8.1 mm to 9.1 mm.
 14. A refrigeration system whosecooling rated capacity is not more than 3.2 kW, said refrigerationsystem comprising a refrigerant circuit (10) which forms a refrigerationcycle in which either a single refrigerant of R32 or a mixed refrigerantwhose R32 contest is not less than 75% is used as a refrigerant andincludes a compressor (ii) which utilizes a resin material as anelectric motor insulating material, wherein said refrigerant circuit(10) includes a gas side pipe (31) which is formed by use of a pipewhose inside diameter is less than 7.92 mm.
 15. A refrigeration systemwhose cooling rated capacity is greater than 32 kW but not more than 5kW, said refrigeration system comprising a refrigerant circuit (10)which forms a refrigeration cycle in which either a single refrigerantof R32 or a mixed refrigerant whose R32 content is not less than 75% isused as a refrigerant and includes a compressor (ii) which utilizes aresin material as an electric motor insulating material, wherein saidrefrigerant circuit (10) includes a gas side pipe (31) which is formedby use of a pipe whose inside diameter is less than 11.1 mm.
 16. Arefrigeration system whose cooling rated capacity is greater than 5 kWbut not more than 9 kW, said refrigeration system comprising arefrigerant circuit (10) which forms a refrigeration cycle in whicheither a single refrigerant of R32 or a mixed refrigerant whose R32content is not less than 75% is used as a refrigerant and includes acompressor (ii) which utilizes a resin material as an electric motorinsulating material, wherein said refrigerant circuit (10) includes agas side pipe (31) which is formed by use of a pipe whose insidediameter is less than 13.88 mm.
 17. A refrigeration system whose coolingrated capacity is greater than 9 kW but not more than 18 kW, saidrefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either a single refrigerant of R32 or amixed refrigerant whose R32 content is not less than 75% is used as arefrigerant and includes a compressor (ii) which utilizes a resinmaterial as an electric motor insulating material, wherein saidrefrigerant circuit (10) includes a gas side pipe (31) which is formedby use of a pipe whose inside diameter is less than 17.05 mm.
 18. Arefrigeration system whose cooling rated capacity is greater than 18 kWbut not more than 22 4 kW, said refrigeration system comprising arefrigerant circuit (10) which forms a refrigeration cycle in whicheither a single refrigerant of R32 or a mixed refrigerant whose R32content is not less than 75% is used as a refrigerant and includes acompressor (11) which utilizes a resin material as an electric motorinsulating material, wherein said refrigerant circuit (10) includes agas side pipe (31) which is formed by use of a pipe whose insidediameter is less than 23.4 mm.
 19. A refrigeration system whose coolingrated capacity is so designed as to be greater than 22.4 kW, saidrefrigeration system comprising a refrigerant circuit (10) which forms arefrigeration cycle in which either a single refrigerant of R32 or amixed refrigerant whose P32 content is not less than 75% is used as arefrigerant and includes a compressor (11) which utilizes a resinmaterial as an electric motor insulating material, wherein saidrefrigerant circuit (10) includes a gas side pipe (31) which is formedby use of a pipe whose inside diameter is less than 26.18 mm.
 20. Arefrigeration system comprising a refrigerant circuit (10) whichincludes (a) a compressor (11) which utilizes a resin material as anelectric motor insulating material and (b) an indoor heat exchanger (15)and forms a refrigeration cycle in which either a single refrigerant ofR32 or a mixed refrigerant whose R32 content is not less than 75% isused as a refrigerant, wherein said indoor heat exchanger (15) includesa heat transfer pipe which is formed by use of a heat transfer pipewhose inside diameter is less than 5.87 mm.
 21. A refrigeration systemcomprising a refrigerant circuit (10) which includes (a) compressor (11)which utilizes a resin material as an electric motor insulating materialand (b) an outdoor heat exchanger (13) and forms a refrigeration cyclein which either a single refrigerant of R32 or a mixed refrigerant whoseR32 content is not less than 75% is used as a refrigerant, wherein saidoutdoor heat exchanger (13) includes a heat transfer pipe which isformed by use of a heat transfer pipe whose inside diameter is less than6.89 mm.
 22. A refrigeration system comprising a refrigerant circuit(10) which includes (a) a compressor (11) which utilizes a resinmaterial as an electric motor insulating material and (b) an outdoorheat exchanger (13) and forms a refrigeration cycle in which either asingle refrigerant of R32 or a mixed refrigerant whose R32 content isnot less than 75% is used as a refrigerant, wherein said outdoor heatexchanger (13) includes a heat transfer pipe which is formed by use of aheat transfer pipe whose inside diameter is less than 7.99 mm.
 23. Therefrigeration system of any one of claims 1–22 wherein said compressor(11) uses a synthetic oil as a refrigeration oil.
 24. The refrigerationsystem of any one of claims 1–13 wherein said liquid side pipe (32) is aliquid side connecting an indoor unit (17) and an outdoor unit (16). 25.The refrigeration system of any one of claims 14–19 wherein said gasside pipe (31) is a gas side connecting pipe for connecting an indoorunit (17) and an outdoor unit (16).
 26. The refrigeration system of anyone of claims 1–22 wherein said mixed refrigerant is an R32/R125 mixedrefrigerant.
 27. The refrigeration system of any one of claims 1–22wherein said refrigerant is a single refrigerant of R32.